1. Field of the Invention
The present invention relates generally to an automobile body structure, and more particularly, to an automobile lower body structure for providing a vehicle body with satisfactory rigidity.
2. Description of the Prior Art
Japanese Utility Model Laid-open Application (unexamined) No. 64-24684 discloses a floor structure in the proximity of a front portion of a passenger compartment. In this floor structure, a front wall and a floor of the passenger compartment are formed by a dashboard lower panel and a floor panel, respectively. The dashboard lower panel is comprised of a vertical partition wall for partitioning the passenger compartment from an engine compartment located frontwardly of the vehicle body and an inclined portion extending rearwardly downwardly from the vertical partition wall. The floor panel is comprised of an upwardly protruding tunnel structure extending longitudinally of the vehicle body and an inclined portion extending frontwardly upwardly from a floor portion. A dashboard lower cross member extending transversely of the vehicle body is secured to the lower surface of the inclined portion to form a reinforcement having a closed cross section, whereas a floor reinforcement extending transversely of the vehicle body is secured to the upper surface of the inclined portion. Furthermore, a dashboard lower reinforcement is secured to the vertical partition wall and the tunnel structure along corner therebetween, and opposite ends of the dashboard lower reinforcement are securely connected to respective of two front frames extending longitudinally of the vehicle body on the lower surface of the floor panel.
However, the above-described conventional floor structure needs a plurality of reinforcements for raising the rigidity thereof at a joining area between the vertical partition wall and the tunnel structure, and a the inclined portion between the vertical partition wall and the floor portion, thus requiring a substantial amount of time for manufacturing the floor structure.
Furthermore, since the tunnel structure is formed by bending the floor panel, the tunnel structure cannot satisfactorily absorb a front-end impact produced, for example, by a head-on collision. Accordingly, this kind of impact load must be absorbed only by front frames extending longitudinally of the vehicle body on both sides thereof. As a result, the problem arises that the front frames must be excessively rigidified or the rigidity must be ensured by enlarging the size of the tunnel structure.